Posted on October 14, 2015 at 03:19Hello,
Let me provide some clarifications and how things will be improved.
We are receiving more and more requests about system_stm32xxx.c file provided within STM32Cube, mainly people are looking to have register access based code for the initialization of
1) system clock at the highest frequency
2) QSPI memory available on ST board
point 1) Was implemented in legacy SPL then removed in the STM32Cube, based on customers feedback who don't want to have the system clock already configured when reaching the main(). As tradeoff, we will provide code for system clock config (based on direct registers access) that will be enabled through compilation switch (disabled by default, up to user to enable it).
for point 2) Generally pre-init configuration is needed to initialize external (SRAM/SDRAM) memory to be used as program data (for heap/stack as example) as extension of the internal SRAM. This is the purpose of CMSIS SystemInit_ExtMemCtl() function.
Of course this could not be the case for QSPI Flash, where it’s rather used for code execution.
However we can extend the purpose of SystemInit_ExtMemCtl() function to provide a compact initialization of the QSPI, coupled w/ system configured at the highest frequency, to implement use case as execute in place. This will shorten the application overall startup time and improve performance.
Updated example will be provided within next version of STM32Cube FW packages.
From other side we are planning other changes to avoid some issues seen recently about the usage of the system_stm32xxx.c template file: this file is provided with implementation of SystemInit_ExtMemCtl() for one target board (usually EVAL board), which needs modification when running on another board.
To resume, below how system_stem32xxxx.c file will be managed within STM32Cube FW
o system_stm32xxxc.c template file provided within STM32 CMSIS drivers
- system running at default clock configuration (typically HSI or MSI
- SystemInit_ExtMemCtl() remains empty
o system_stm32xxxc.c user file provided within FW examples: will provide custom file per board (within Projects\<board_name>\Templates) , where
- system running at max clock frequency, activated through compilation switch
- SystemInit_ExtMemCtl() remains empty if no external SDRAM/SRAM/QSPI available on board
- SystemInit_ExtMemCtl() updated to configure external SDRAM/SRAM/QSPI available on board, activated through compilation switch
Feel free to share your feedback.
Jasmin.
Sorry, it's just a little frustrating, the code is going to end up in thousands of devices, you have to be more careful, the Microsoft method of fixing some things, breaking others, with perpetual software releases doesn't work well in embedded.
